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at its origin, the two halves re-uniting at the elbow-joint, and then dividing into the radial and ulnar arteries in the usual manner. In the second case an aberrant artery was given off from the radial side of the brachial artery, again almost at its origin. This aberrant artery anastomosed below the elbow-joint with the radial side of the radial artery. In each of these cases the right and left sides varied in precisely the same manner.

Thirdly, as to pathology. Mr. James Paget, speaking of symmetrical diseases, says: “A certain morbid change of structure on one side of the body is repeated in the exactly corresponding part of the other side.” He then quotes and figures a diseased lion's pelvis from the College of Surgeons Museum, and says of it: “Multiform as the pattern is in which the new bone, the product of some disease comparable with a human rheumatism, is deposited—a pattern more complex and irregular than the spots upon a map-there is not one spot or line on one side which is not represented, as exactly as it would be in a mirror, on the other. The likeness has more than daguerreotype exactness. He goes on to observe: “I need not describe many examples of such diseases. Any out-patients' room will furnish abundant instances of exact symmetry in the eruptions of eczema, lepra, and psoriasis ; in the deformities of chronic rheumatism, the paralyses from lead ; in the eruptions excited by iodide of potassium or copaiba, And any large museum will contain examples of equal symmetry in syphilitic ulcerations of the skull; in rheumatic and syphilitic deposits on the tibia and other bones ; in all the effects of chronic rheumatic arthritis, whether in the bones, the ligaments, or the cartilages;

1 “Lectures on Surgical Pathology," 1853, vol. i. p.

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in the fatty and earthy deposits in the coats of arteries.”

He also considers it to be proved that, “Next to the parts which are symmetrically placed, none are so nearly identical in composition as those which are homologous. For example, the backs of the hands and of the feet, or the palms and soles, are often not only symmetrically, but similarly, affected with psoriasis. So are the elbows and the knees; and similar portions of the thighs and the arms may be found affected with ichthyosis. Sometimes also specimens of fatty and earthy deposits in the arteries occur, in which exact similarity is shown in the plan, though not in the degree, with which the disease affects severally the humeral and femoral, the radial and peroneal, the ulnar and posterior tibial arteries.”

Dr. William Budd2 gives numerous instances of symmetry in disease, both lateral and serial. Thus, amongst others, we have one case (William Godfrey) in which the hands and feet were distorted. “ The distortion of the right hand is greater than that of the left, of the right foot greater than that of the left foot.” In another (Elizabeth Alford) lepra affected the extensor surfaces of the thoracic and pelvic limbs. Again, in the case of skin disease illustrated in Plate III., “The analogy between the elbows and knees is clearly expressed in the fact that these were the only parts affected with the disease.”3

Professor Burt Wilder,4 in his paper on “ Pathological 1 “Lectures on Surgical Pathology,” 1853, vol. i. p. 22.

2 See “Medico-Chirurgical Transactions,” vol. xxv. (or vii. of 2nd series), 1842, p. 100, Pl. III.

3 Ibid., p. 122. 4 See Boston Medical and Surgical Journal for April 5, 1866, vol. lxxiv.

p. 189.

Polarities,” strongly supports the philosophical importance of these peculiar relations, adding arguments in favour of antero-posterior homologies, which it is here unnecessary to discuss, enough having been said, it is believed, to thoroughly demonstrate the existence of those deep internal relations which are named lateral and serial homologies.

What explanation can be offered of these phenomena? To say that they exhibit a “nutritional relation ” brought about by a “ balancing of forces” is no explanation of the fact. The changes are, of course, brought about by a “nutritional” process, and the symmetry is undoubtedly the result of a “balance of forces," but to say so is a truism. The question is, what is the cause of this “nutritional balancing”? It is here contended that this “balancing” must be due to an internal cause which at present science is utterly incompetent to explain. It is an internal property possessed by each living organic whole as well as by each non-living crystalline mass, and that there is such internal power or tendency, which may be termed a “polarity," seems to be demonstrated by the instances above given, which can easily be multiplied indefinitely. Mr. H Spencer(speaking of the reproduction, by budding, of a Begonia-leaf) recognizes a power of the kind. He says:

We have therefore no alternative but to say, that the living particles composing one of these fragments, have an innate tendency to arrange themselves into the shape of the organism to which they belong. We must infer that a plant or animal of any species, is made up of special units, in all of which there dwells the intrinsic aptitude to aggregate into the form of that species : just as in the

1 “Principles of Biology,” vol. i p. 180.

atoms of a salt, there dwells the intrinsic aptitude to crystallize in a particular way. It seems difficult to conceive that this can be so; but we see it is so.”

..."For this property there is no fit term. If we accept the word polarity, as a name for the force by which inorganic units are aggregated into a form peculiar to them; we may apply this word to the analogous force displayed by organic units.” 1

Dr. Jeffries Wyman, in his paper on the “Symmetry and Homology of Limbs,” has a distinct chapter on the

Analogy between Symmetry and Polarity,” illustrating it by the effects of magnets on “particles in a polar condition.”

Mr. J. J. Murphy, after noticing the power which crystals have to repair injuries inflicted on them and the modifications they undergo through the influence of the medium in which they may be formed, goes on to say:4 “ It needs no proof that in the case of spheres and crystals the forms and the structures are the effect, and not the cause, of the formative principles. Attraction, whether gravitative or

1 Mr. Spencer, in an appendix to the first volume of the “Principles of Biology,” has explained more fully what he means by the word “innate.” He attributes “imnate tendencies" entirely to the inherited structures of the "physiological units” produced in them by the total forces of the organisms through which they have been transmitted during the serial evolution of such organisms. This, however, is a mere moving of the difficulty a step backwards ; and he by no means gets rid of (what never can be got rid of) the conception of innate power—of force proceeding from the organism as distinguished from force proceeding towards the organism. At the very least, Mr. Spencer must attribute to his ultimate units an innate power of inheriting effects of ancestral modifications, and this is, in principle, a power fully as mysterious as any for which the author of this book here contends.

2 See the “Proceedings of the Boston Society of Natural History,” vol. xi. June 5, 1867. 3 “Habit and Intelligence,” vol. i. p. 75.

4 Ibid. p. 112.

capillary, produces the spherical form; the spherical form does not produce attraction. And crystalline polarities produce crystalline structure and form ; crystalline structure and form do not produce crystalline polarities. The same is not quite so evident of organic forms, but it is equally true of them also.” ... “ It is not conceivable that the microscope should reveal peculiarities of structure corresponding to peculiarities of habitual tendency in the embryo, which at its first formation has no structure whatever ;”1 and he adds that “there is something quite inscrutable and mysterious” in the formation of a new individual from the germinal matter of the embryo. In another place? he says: “We know that in crystals, notwithstanding the variability of form within the limits of the same species, there are definite and very peculiar formative laws, which cannot possibly depend on anything like organic functions, because crystals have no such functions ; and it ought not to surprise us if there are similar formative or morphological laws among organisms, which, like the formative laws of crystallization, cannot be referred to any relation of form or structure to function. Especially, I think, is this true of the lowest organisms, many of which show great beauty of form, of a kind that appears to be altogether due to symmetry of growth; as the beautiful star-like rayed forms of the acanthometra, which are low animal organisms not very different from the Foraminifera." Their " definiteness of form does not appear to be accompanied by any corresponding differentiation of function between different parts; and, so far as I can see, the beautiful regularity and symmetry of their radiated forms are altogether due to unknown laws 1 “Habit and Intelligence,” vol. i. p. 170.

2 Ibid. p. 229,

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